After the full CVA21 injection schedule has been completed, patients will be followed at 12-weekly intervals beginning on Day 169 for a total of 12 months according to the schedule for safety assessment and indefinitely for survival. Patients with progressive disease (but without rapid clinical deterioration) at 6 months (Day 169) will have a further tumor assessment 6 weeks later for confirmation or continuation of observation for duration of disease control and all subjects will be followed for survival. Patients who are withdrawn from treatment with CVA21 during the treatment phase must also be followed up every 6 weeks for 12 weeks for safety and for survival.